The present invention relates to a pharmaceutical composition comprising as an active ingredient at least one compound selected from the group consisting of the derivatives of N-(dihydroxybenzylidene)amino acid represented by the formula (I): ##STR3## wherein R represents an alkylene group having one to five carbon atoms, a phenylene group or ##STR4## the pharmaceutically acceptable salts and esters thereof, and a pharmaceutically acceptable carrier therefor, and to a method for treating nephritis which comprises administering to a patient suffering from nephritis a pharmaceutically effective amount of a compound selected from the group consisting of the derivatives of N-(dihydroxybenzylidene)amino acid, represented by the formula (I): ##STR5## wherein R represents an alkylene group having one to five carbon atoms, a phenylene group or ##STR6## or the pharmaceutically acceptable salts and esters thereof.
The present inventors have already found that the compound represented by the formula (I) wherein R represents ##STR7## is useful as a medicine and is effective for treatment of auto-immune diseases such as rheumatoid arthritis and systemic lupus erythematosus (refer to Japanese Patent Applications Laid-Open No. 57-116035 (1982) and No. 57-140714 (1982)). Thereafter, as a result of the present inventors' studies on the action of the compounds represented by the formula (I) on human nephritis, it has been found by the present inventors that the compounds represented by the formula (I) inhibit the glomerulonephritis which is regarded as a disease caused by an immuno-complex, and is effective as a medicine for treating nephritis.
Although the cause of diseases due to immunocomplexes such as nephritis is complicated and there are many points not yet elucidated therein, it is considered that the complex of an antigen and an antibody deposit on the glomeruli releasing various chemical mediators which cause disturbance in the renal tissue.
The present inventors have found out that administration of the compounds represented by the formula (I) to a MRL/1 mouse which is an animal naturally suffering from an auto-immune disease suppresses the deposition of immunocomplexes in the glomeruli of the mouse with inhibition of the hyperplastic nephritis such as basement membrane thickening. The present inventors have also found that the above-mentioned compounds clinically reduces the concentration of proteins in the urine of the mouse and that the BSA-nephritis, which is caused by intravenous injection of bovine serum (BSA) into a rabbit, is remarkably improved by the compounds represented by the formula (I), and thus the present inventors have attained the present invention.